Tryit Editor v1.8

Source Code:

<!DOCTYPE html>
<html>
<head>
<script type="text/vbscript">

sub mySub()
MsgBox("Hello" & chr(13) & "world")
end sub

</script>
</head>
<body>

<button onclick="mySub()">Click to get a messagebox with line feed.</button>

</body>
</html>

Result:

W3Schools.com - Try it yourself

Edit the code above and click "Submit Code" to see the result.